arXiv subjects

Xuan Luo

Publications and source records attributed to Xuan Luo.

At least 55 records · Page 3Linked to original sources

arXiv2025

The bound and resonant states of $D^{()}D^{()}$ and $D^{()}\bar{D}^{()}$ with the complex scaling method

We perform a systematic study of the possible molecular states composed of a pair of heavy mesons such as $D^{(*)}D^{(*)}$, $D^{(*)}\bar{D}^{(*)}$ in the framework of the one-boson-exchange model. The exchanged bosons include the pseudoscalar, scalar and vector mesons($π$, $σ$, $ρ$, $ω$). We use the Bonn approximation to get the interaction potential of one-boson-exchange model, then apply the complex scaling method to calculate the bound and resonant states. The results indicate that the $D^{(*)}D^{(*)}$ and $D^{(*)}\bar{D}^{(*)}$ system can not only form several bound states, but also a P-wave resonant state. The hadron molecular state model can explain the structure of $T_{cc}^+$ as a bound state $DD^{*}$ with quantum number $I(J^P) = 0(1^+)$. In addition, we also discovered other bound and resonant states, which have the potential to be observed experimentally.

hep-ph↗

arXiv2025

Topped baryons from QCD sum rules

The recent CMS observation of a near-threshold enhancement in top quark pair production provides the first experimental indication of a short-lived pseudoscalar $t\bar{t}$ bound state, commonly referred to as toponium. While most existing studies focus on toponium using perturbative QCD near threshold, baryonic configurations containing a single top quark -- singly topped baryons -- offer a complementary nonperturbative perspective. Notably, singly topped baryons are expected to exhibit a longer lifetime and a narrower decay width than toponium, since only one top quark decays rather than two. The heavy quark effective theory provides a natural and powerful framework for analyzing such systems, allowing the separation of heavy and light quark dynamics. In this work we employ heavy quark effective theory to investigate the internal structure of ground-state singly topped baryons. We construct their interpolating currents and analyze them using QCD sum rules. The resulting masses of the ground-state singly topped baryons are found to lie around 174 GeV, approximately $1.1$-$1.5$ GeV above the pole mass of the top quark.

hep-ph↗

arXiv2025

Theoretical study of the $N(1535)$ in the process $Λ_c^+\to nπ^+π^0$

We have investigated the $Λ_c^+\to nπ^+π^0$ decay process using the chiral unitary approach, by considering that the nucleon resonance $N(1535)$ could be dynamically generated through $S$-wave pseudoscalar meson-octet baryon interactions. In the invariant mass distributions of $π^0n$ and $π^+n$, we observe a distinct peak structure associated with the resonance states $N(1535)^0$ and $N(1535)^+$, respectively. Our results suggest that the $Λ_c^+\to nπ^+π^0$ process can be utilized to probe the properties of the nucleon $N(1535)$, and therefore, we encourage more precise experimental measurements of this process in the future.

hep-ph↗

arXiv2025

Solving two and three-body systems with deep neural networks

We develop a new method for solving two- and three-body bound state problems using unsupervised machine learning techniques. We use a deep neural network to calculate both simple and realistic potentials, obtaining the properties of the deuteron and triton bound states for the chiral effective field theory NN potential. Our results provide significant accuracy with no prior assumptions about the behaviour of the wave function. This neural network technique, which extends from two-body to three-body, may provide insight into potential solutions to the nuclear and hadronic many-body problems.

hep-ph↗

arXiv2025

Direct observation of distinct bulk and edge nonequilibrium spin accumulation in ultrathin MoTe$_2$

Low-symmetry two-dimensional (2D) topological materials such as MoTe$_2$ host efficient charge-to-spin conversion (CSC) mechanisms that can be harnessed for novel electronic and spintronic devices. However, the nature of the various CSC mechanisms and their correlation with underlying crystal symmetries remain unsettled. In this work, we use local spin-sensitive electrochemical potential measurements to directly probe the spatially dependent nonequilibrium spin accumulation in MoTe$_2$ flakes down to four atomic layers. We are able to clearly disentangle contributions originating from the spin Hall and Rashba-Edelstein effects and uncover an abundance of unconventional spin polarizations that develop uniquely in the sample bulk and edges with decreasing thickness. Using ab-initio calculations, we construct a unified understanding of all the observed CSC components in relation to the material dimensionality and stacking arrangement. Our findings not only illuminate previous CSC results on MoTe$_2$ but also have important ramifications for future devices that can exploit the local and layer-dependent spin properties of this 2D topological material.

cond-mat.mes-hall↗

arXiv2025

Radiative decays of $P$-wave charmed baryons in the $SU(3)$ flavor $\bf6_F$ representation

We perform a comprehensive investigation of the radiative decays of $P$-wave charmed baryons in the $SU(3)$ flavor $\mathbf{6}_F$ representation, employing the light-cone QCD sum rule approach within the framework of heavy quark effective theory. We analyze their electromagnetic transitions into ground-state charmed baryons via photon emission. When combined with the mass spectra and strong decay properties previously studied in Ref.~\cite{Yang:2021lce}, our results constitute a systematic and complete QCD sum rule analysis of the $P$-wave singly charmed baryons within the framework of heavy quark effective theory. As summarized in Table~\ref{tab:result}, several excited charmed baryons are found to possess suppressed strong decay widths, thereby rendering their radiative decay channels particularly significant for experimental identification and theoretical understanding.

hep-ph↗

arXiv2025

$P$-wave single charmed baryons of the $SU(3)$ flavor $\bf\bar3_F$

We study the $P$-wave single charmed baryons of the $SU(3)$ flavor $\bf\bar3_F$ within the framework of heavy quark effective theory. We systematically calculate their strong and radiative decay properties using the light-cone sum rule method. Besides the $Λ_c(2595)$, $Λ_c(2625)$, $Ξ_c(2790)$, and $Ξ_c(2815)$, our results suggest the existence of two additional $Λ_c$ baryons and two additional $Ξ_c$ baryons. Their masses, mass splittings within the same multiplets, and decay properties are summarized in Table V for future experimental searches.

hep-ph↗

arXiv2025

Magnetic phase diagram of Cr2Te3 revisited by ac magnetostrictive coefficient

Two-dimensional (2D) magnetic materials have attracted considerable interest owing to their potential applications in spintronics and fundamental investigations into low-dimensional magnetism. Cr2Te3, a quasi 2D non van der Waals magnet, exhibits a complex magnetic phase diagram due to competing magnetic interactions within and between layers. However, the precise nature and evolution of these magnetic phases remain unclear. Here, we utilize an ultrahigh-sensitive composite magnetoelectric technique, which probes the ac magnetostrictive coefficient, to systematically explore the temperature magnetic field phase diagram of Cr2Te3 single crystals. Our results reveal the coexistence of multiple magnetic phases, including canted ferromagnetic, antiferromagnetic, and paramagnetic states. Another canted ferromagnetic phase and a possible triple point have been proposed. The updated phase diagram provides deeper insights into the specific spin configurations associated with each phase. These findings also highlight the decoupled magnetic ordering between the Cr1/Cr3 layers and the Cr2 layer near the magnetic ordering temperature.

cond-mat.mtrl-sci↗

arXiv2025

Strong decay properties of P-wave single bottom baryons of the SU(3) flavor antitriplet $\bf\bar 3_F$

We study the $P$-wave bottom baryons of the $SU(3)$ flavor antitriplet and systematically calculate their strong decay properties, including their $D$-wave decays into ground-state bottom baryons with light pseudoscalar mesons and $S$-wave decays into ground-state bottom baryons with light vector mesons. Together with Refs.~\cite{Tan:2023opd,Yang:2019cvw,Yang:2020zrh,Luo:2024jov}, a rather complete investigation has been performed to study their mass spectra and strong/radiative decay properties, through the methods of QCD sum rules and light-cone sum rules within the framework of heavy quark effective theory. Among various possibilities, we identify four $Λ_b$ and four $Ξ_b$ baryons, with limited decay widths and so capable of being observed in experiments. Their masses, mass splittings within the same multiplets, and strong/radiative decay widths are summarized in Table~\ref{tab:decayb3f} for future experimental searching.

hep-ph↗

arXiv2025

Probing double hadron resonance by complex momentum representation method

Resonances are ubiquitous phenomena in nature, and physicists have developed many methods to explore resonant states. Of particular note is the complex momentum representation(CMR) method, which has been developed and widely used in the study of resonant states in atomic, molecular and nuclear physics. Here, for the first time, we have developed this novel method to study hadron resonant states. The CMR method is applied to probe the bound and resonant states for the $Λ_cD(\bar{D})$ and $Λ_cΛ_c(\barΛ_c)$ systems, in which the resonant states are exposed clearly in complex momentum plane and the resonance parameters can be determined precisely without imposing unphysical parameters. The results show that the CMR method has achieving higher accuracy than other widely used methods. This method is not only very effective for narrow resonances, but also can be reliably applied to broad resonances.

hep-ph↗

arXiv2025

Radiative decays of $P$-wave bottom baryons from light-cone sum rules

We carry out a comprehensive investigation on the radiative decays of $P$-wave bottom baryons using the light-cone sum rule method. We analyze their electromagnetic transitions into ground-state bottom baryons together with a photon. Together with their mass spectra and strong decays investigated in Refs. \cite{Yang:2020zrh,Tan:2023opd}, a rather complete QCD sum rule study has been done to understand the $P$-wave singly bottom baryons within the framework of heavy quark effective theory. As summarized in Tables~\ref{tab:candidate}/\ref{tab:candidate6f}, some $P$-wave bottom baryons have limited strong decay widths so that their radiative decay widths become non-negligible. We propose to study these excited bottom baryons and their radiative decays in the future Belle-II, BESIII, and LHCb experiments.

hep-ph↗

arXiv2025

Can Many-Shot In-Context Learning Help LLMs as Evaluators? A Preliminary Empirical Study

Utilizing Large Language Models (LLMs) as evaluators to assess the performance of LLMs has garnered attention. However, this kind of evaluation approach is affected by potential biases within LLMs, raising concerns about the accuracy and reliability of the evaluation results of LLMs. To address this problem, we propose and study two many-shot In-Context Learning (ICL) prompt templates to help LLM evaluators mitigate potential biases: Many-Shot with Reference (MSwR) and Many-Shot without Reference (MSoR). Specifically, the former utilizes in-context examples with model-generated evaluation rationales as references, while the latter does not include these references. Using these prompt designs, we investigate the impact of increasing the number of in-context examples on the consistency and quality of the evaluation results. Experimental results show that advanced LLMs, such as GPT-4o, perform better in the many-shot regime than in the zero-shot and few-shot regimes. Furthermore, when using GPT-4o as an evaluator in the many-shot regime, adopting MSwR as the prompt template performs better than MSoR.

cs.CL↗

arXiv2025

Interlayer Hopping between Surface Mott Insulator and Bulk Band Insulator in layered 1T-TaS_{2}

In condensed matter physics, various mechanisms give rise to distinct insulating phases. The competition and interplay between these phases remain elusive, even for the seemingly most distinguishable band and Mott insulators. In multilayer systems, such interplay is mediated by interlayer hopping, which competes with the Coulomb repulsion to determine the nature of insulators. The layered compound 1T-TaS_{2} provides an ideal platform for investigating this phenomenon, as it naturally hosts coexisting Mott and band insulating states. However, distinguishing these distinct insulating states and characterizing the evolution remain challenging. In this study, we employ a dual approach utilizing surface-sensitive High-Resolution Electron Energy Loss Spectroscopy (HREELS) and bulk-sensitive Fourier-transform Infrared Spectroscopy (FTIR) to investigate the electronic excitation spectrum of 1T-TaS_{2}. Our methodology effectively identifies the features originating from the Mott and band insulators by analyzing the differences in their bulk and surface spectral weights, along with their energy distinctions. Based on the previous identification, we further investigate the evolution of insulating state features in the homostructure as they are modulated by temperature. The measurements and Dynamical Mean-Field Theory (DMFT) calculations suggest that the softening and broadening of Hubbard excitations in the Mott state with increasing temperature result from enhanced interlayer hopping between the Mott and band insulators.

cond-mat.mtrl-sci↗

arXiv2024

Counting-Stars: A Multi-evidence, Position-aware, and Scalable Benchmark for Evaluating Long-Context Large Language Models

Despite recent efforts to develop large language models with robust long-context capabilities, the lack of long-context benchmarks means that relatively little is known about their performance. To alleviate this gap, in this paper, we propose \textbf{Counting-Stars}, a multi-evidence, position-aware, and scalable benchmark designed to evaluate the multi-evidence retrieval capabilities of long-context LLMs. \textbf{Counting-Stars} comprises two counting-based multiple pieces of evidence retrieval sub-tasks: searching and reasoning. Using Counting-Stars, we conduct experiments to evaluate several long-context LLMs, including GPT-4 Turbo, Gemini 1.5 Pro, Claude3 Opus, GLM-4, and Moonshot-v1. Extensive experimental results demonstrate that Gemini 1.5 Pro achieves the best overall results, while GPT-4 Turbo exhibits the most stable performance across various tasks. Furthermore, our analysis of these LLMs, which have been extended to handle long-context scenarios, indicates that significant room for improvement remains as the length of the input context and the complexity of the tasks increase.

cs.CL↗

arXiv2024

A CNN-based particle tracking method for large-scale fluid simulations with Lagrangian-Eulerian approaches

A novel particle tracking method based on a convolutional neural network (CNN) is proposed to improve the efficiency of Lagrangian-Eulerian (L-E) approaches. Relying on the successive neighbor search (SNS) method for particle tracking, the L-E approaches face increasing computational and parallel overhead as simulations grow in scale. This issue arises primarily because the SNS method requires lengthy tracking paths, which incur intensive inter-processor communications. The proposed method, termed the CNN-SNS method, addresses this issue by approximating the spatial mapping between reference frames through the CNN. Initiating the SNS method from CNN predictions shortens the tracking paths without compromising accuracy and consequently achieves superior parallel scalability. Numerical tests demonstrate that the CNN-SNS method exhibits increasing computational advantages over the SNS method in large-scale, high-velocity flow fields. As the resolution and parallelization scale up, the CNN-SNS method achieves reductions of 95.8% in tracking path length and 97.0% in computational time.

physics.comp-ph↗

arXiv2024

Multiple magnetic orders discovered in the superconducting state of EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$

The interplay between superconductivity and magnetism is an important subject in condensed matter physics. EuFe$_{2}$As$_{2}$-based iron pnictides could offer an interesting plateau to study their relationship that has attracted considerable attention. So far, two magnetic phase transitions were observed in EuFe$_{2}$As$_{2}$-based crystal, which were deemed to originate from the itinerant Fe moments ($\sim$ 190 K) and the localized Eu$^{2+}$ moments ($\sim$ 19 K), respectively. Here, we systematically studied the heat capacity for the EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ crystals with \textit{x} = 0.21 (optimally doped) and \textit{x} = 0.29 (overdoped). We have found two new magnetic orders in the superconducting state (ranging from 0.4 to 1.2 K) in the optimally doped crystal. As more P was introduced into the As site, one of the magnetic orders becomes absent in the overdoped crystal. Additionally, we observed strong field and orientation dependence in heat capacity. The present findings in EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ have detected the new low-temperature magnetic orders, which may originate from the localized Eu$^{2+}$ spins order or the spin reorientation.

cond-mat.supr-con↗

arXiv2024

Quark: Real-time, High-resolution, and General Neural View Synthesis

We present a novel neural algorithm for performing high-quality, high-resolution, real-time novel view synthesis. From a sparse set of input RGB images or videos streams, our network both reconstructs the 3D scene and renders novel views at 1080p resolution at 30fps on an NVIDIA A100. Our feed-forward network generalizes across a wide variety of datasets and scenes and produces state-of-the-art quality for a real-time method. Our quality approaches, and in some cases surpasses, the quality of some of the top offline methods. In order to achieve these results we use a novel combination of several key concepts, and tie them together into a cohesive and effective algorithm. We build on previous works that represent the scene using semi-transparent layers and use an iterative learned render-and-refine approach to improve those layers. Instead of flat layers, our method reconstructs layered depth maps (LDMs) that efficiently represent scenes with complex depth and occlusions. The iterative update steps are embedded in a multi-scale, UNet-style architecture to perform as much compute as possible at reduced resolution. Within each update step, to better aggregate the information from multiple input views, we use a specialized Transformer-based network component. This allows the majority of the per-input image processing to be performed in the input image space, as opposed to layer space, further increasing efficiency. Finally, due to the real-time nature of our reconstruction and rendering, we dynamically create and discard the internal 3D geometry for each frame, generating the LDM for each view. Taken together, this produces a novel and effective algorithm for view synthesis. Through extensive evaluation, we demonstrate that we achieve state-of-the-art quality at real-time rates. Project page: https://quark-3d.github.io/

cs.CV↗

arXiv2024

The Theoretical Study of $p\bar{p}\to\barΛΣη$ Reaction

We study the production of hyperon resonances in the $p\bar{p}\to\barΛΣη$ reaction within an effective Lagrangian approach. The model includes the production of $Σ(1750)$ and $Λ(1670)$ in the intermediate state excited by the $K$ and $K^*$ meson exchanges between the initial proton and antiproton. Due to the large coupling of $Σ(1750)Ση$ vertex, $Σ(1750)$ is found a significant contribution near the threshold in this reaction. We provide total and differential cross section predictions for the reation and discuss the possible influence of $Σ(1750)Ση$ vertex coupling and model parameters, which will be useful in future experimental studies. This reaction can provide a platform for studying the features of $Σ(1750)$ resonance, especially the coupling to $Ση$ channel.

hep-ph↗